Today, globally, several types of cellular networks co-exist, like GSM (Global System for Mobile communications), WCDMA (Wideband Code Division Multiple Access), LTE (Long Term Evolution), and TDSCDMA (Time Division Synchronous Code Division Multiple Access) etc. To work seamlessly with this multiple radio access technology (RAT) network environment, mobile vendors are making mobile phones, supporting legacies as well as upcoming systems. GSM being one of the most widely deployed and used as legacy system, the support of GSM Radio Access Technology (RAT) is by-default provided in most of the Multi-RAT Mobile devices and also at the same time covered by most of the networks worldwide. Even though there are new technologies, such as LTE being deployed, there will still be LTE network coverage holes, where Mobile devices have to quickly find out the presence of GSM/legacy RAT cells and connect to the GSM/Legacy RAT network for to maintain packet switched or circuit switched calls or to be remained connected with the PLMNs (public land mobile networks).
In “An efficient monitoring strategy for intersystem handover from TD-SCDMA to GSM networks”, by Durastante G, et al, in IEEE conference on Personal, Indoor and Mobile Radio Communications 2002, intersystem handover between third and second generation mobile radio systems is considered. In such a handover the user equipment has to know the timing and slot structure of a target GSM cell, which is only possible during a GSM cell-reconfiguration. US2011/280141 proposes a method to create discontinues reception (DRX) for GSM cell search before handover. This method is also dependent on a pre-known time slot structure of a GSM cell.
U.S. Pat. No. 6,587,695 proposes a method to reduce initial cell search time and distinguish between 51 and 52 multi-frames. The proposed method would require a standard change.